1. Field of the Invention
The present invention relates generally to a method of producing visibly transparent conductive coatings, substantially optically transparent, on substrates at low temperature and, more particularly, to a method of producing transparent conductive coatings of metal oxides on plastic materials by the utilization of a glow discharge process.
2. Description of the Prior Art
In the prior art, metallic oxide layers have been produced on a variety of substrates by several techniques including vacuum evaporation. However, this type of process requires a high temperature, high vacuum environment which necessitates expensive precision equipment and cannot be used to coat plastic substrates simply because the substrates cannot survive the process. Another technique involving cathode sputtering has been used. This too is an expensive method requiring a great deal of input energy and considerable time to achieve a reasonable layer thickness.
The use of some organo-metallic compounds to provide the metal component of a desired coating utilizing low pressure glow discharge to activate the monomer is generally disclosed in the prior art. U.S. Pat. No. 3,243,363 to Helwig, issued Mar. 29, 1966, shows the use of compounds such as tetraethyl lead Pb(C.sub.2 H.sub.5).sub.4 and silicium hexamethyl (H.sub.3).sub.3.Si-Si.(CH.sub.3).sub.3 in a two-electrode glow discharge system to plate a metallic layer on the substrate and the use of metallic carbonyl compounds such as iron pentacarbonyl Fe(CO).sub.5 and nickel tetracarbonyl Ni(CO).sub.4 to deposit a dielectric layer of the oxide of the carbonyl-forming metal on a selected substrate. That reference, however, is limited to the deposition of metal and dielectric films used generally for the production of capacitance devices.